Semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices that in the past comprised only mechanical components now have electronic parts that require semiconductor devices, for example.
Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor substrate or wafer, and patterning the various material layers using lithography. The material layers typically comprise thin films of conductive, semiconductive, and insulating materials that are patterned and etched to form integrated circuits (IC's). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip, for example.
Isolation regions are used to provide electrical isolation between active areas or electronic components formed on an integrated circuit. Shallow trench isolation (STI) and deep trench (DT) isolation are examples of some types of isolation regions that are widely used in semiconductor devices.
STI regions are often used in complementary metal oxide semiconductor (CMOS) devices, which use both positive and negative channel devices in complementary configurations. The positive and negative channel devices of a CMOS device are typically referred to as a p channel metal oxide semiconductor (PMOS) transistor and an n channel metal oxide semiconductor (NMOS) transistor. The PMOS transistor is formed in an n well (e.g., a well implanted with n type dopants) and the NMOS transistor is formed in a p well, for example. An STI region is usually formed between the n well and p well of the PMOS transistor and the NMOS transistor, respectively. The STI region usually extends within a semiconductor substrate by about the depth of the maximum n well and p well doping concentration, e.g., by about 0.2 to 1.0 μm, for example.
In memory devices, STI regions are used to separate the element regions of a memory array, e.g., such as an array of dynamic random access memory (DRAM) cells. The element regions may include active areas, storage capacitors, and other electronic devices such as transistors. In some designs, STI regions define the bitline contact landing area in a vertical DRAM cell. The STI regions also prevent cross-talk between two neighboring DRAM cells connected via the same wordline, for example, which ensures that only one cell is modified when being written to by accessing one row and a corresponding column in the DRAM array, for example. STI regions are also used in other types of memory devices, such as static random access memory (SRAM) devices.
To form isolation regions, trenches are usually formed in a substrate or workpiece, and the trenches are filled with one or more insulating materials. Etch processes and chemical mechanical polishing (CMP) processes are typically used to remove excess insulating material from the top surface of the substrate.
One problem that often occurs in the formation of isolation regions is the formation of recesses or voids in the insulating material used to fill the trenches. The lack of insulating material in the recessed or voided areas can result in inadequate electrical isolation between active areas, and can result in shorts if conductive material is subsequently deposited in the recessed or void areas. Furthermore, it is generally desirable for the topography of the top surface of a substrate to be planar, to improve subsequent lithography and CMP processes, for example.
As semiconductor device features are decreased in size, as is the trend in the industry, high aspect ratio trenches are more frequently used, wherein the depth of the trenches is greater than the width, for example. Void formation is frequently a problem in isolation regions formed in trenches having a high aspect ratio.
Thus, what are needed in the art are improved methods of forming isolation regions of semiconductor devices.